1. Field of the Invention
The present invention relates to a tape reproduction apparatus and method for reproducing and outputting a mark pattern recorded in parallel to a magnetic tape.
2. Description of the Related Art
A conventional tape reproduction apparatus using a magnetic tape as a recording medium is also used for a data recording in a computer system. The magnetic tape and the tape reproduction apparatus have simple configurations and cost not much. The magnetic tape can be used for recording a plurality of data items in parallel to one another in a plurality of tracks.
There are various types of magnetic tapes for recording a data processed in a computer system. For example a 18-track product is widely spread. The 18-track magnetic tape is usually divided into six zones, each consisting of three tracks as shown below.
TABLE 1 Track Zone 1 A 2 B 3 C 4 D 5 E 6 F 7 A 8 B 9 C 10 D 11 E 12 F 13 A 14 B 15 C 16 D 17 E 18 F
On the other hand, a plurality of types of mark patterns recorded on the aforementioned magnetic tape consist of 6 bits. The 6-bit binary data is recorded in parallel in the six zone. The binary data thus recorded is called a tone signal and all one signal. The tone signal is a serial 6 bits of "100000" and the all one signal is a serial 6 bits of "111111".
However, this has no direct relation to the present invention. Hereinafter, for the 6 bits of the mark pattern are related to 6 data tracks of the magnetic tape. The binary data constituting a mark pattern will be explained simply as a tone signal and all one signal.
Here, a conventional tape reproduction apparatus having the aforementioned configuration will be explained with reference to FIG. 6. FIG. 6 is a block diagram showing a conventional tape reproduction apparatus. The tape reproduction apparatus 100 has a tape drive block 101, which is connected via an analog/digital (A/D) conversion circuit 102 to a signal generation circuit 103.
The signal generation circuit 103 is connected to a mark detection circuit 104, which is connected to five mark length counters 105 for accumulating time values. That is, as shown in FIG. 7, five mark patterns are recorded on the magnetic tape as different binary data items. Corresponding to these mark patterns, five mark length counters 105 are provided.
It should be noted that the aforementioned five mark patterns are DID (density identity), IDS (identity separator), IBG (inter block gap), TM (tape mark), and ERG (erase gap).
Each of the five mark length counters 105 is connected to a corresponding comparison circuit 106 serving as mark confirmation blocks. These comparison circuits 106 are connected to a microcomputer 107.
It should be noted that this tape reproduction apparatus 100 also includes a clock circuit (not depicted), which is connected to the aforementioned circuits 103 to 106.
The tape drive block 101 includes a tape drive mechanism and a magnetic head (not depicted). This magnetic head, the A/D conversion circuit 102, and the signal generation circuit 103 constitute a data reproduction block. The tape drive mechanism has a drive motor and a tape role up reel. As has been explained above, the magnetic tape (not depicted) is linearly moved on the 6 tracks (actually 18 tracks).
The magnetic head reads the six data tracks in parallel and the A/D conversion circuit 102 convert in serial respective analog signals into digital signals. If the serial digital signal is "100000", the signal generation circuit 103 generates the tone signal which is one of the binary data, in synchronization with a reference signal of the clock circuit. Otherwise, the signal generation circuit generates the other of the binary data, i.e., the all one signal.
The mark detector circuit 104 successively identifies five mark patterns in the six parallel binary data successively generated in serial, and upon identification, transmits an enable signal to a corresponding mark length counter 105. The mark length counter integrates the input time as a reproduction time of the mark pattern by a reference clock.
In each of the comparison circuits 106, a predetermined reference time is set in advance assuming "90%" of the ANSI (American National Standards Institute). When a reproduction time integrated by the corresponding mark length counter 105 connected has reached the reference time, the comparison circuit confirms its mark pattern and outputs a detection signal to the microcomputer.
It should be noted that a recording time in the magnetic tape differs depending on the mark pattern type and accordingly, the aforementioned reference time is set for each of the mark patterns. Consequently, the aforementioned tone signal of "100000" and the all one signal of "111111" are repeatedly recorded on the magnetic tape by a predetermined number of times for each of the mark patterns.
The microcomputer 107 includes a CPU (central processing unit) a ROM (read only memory) and RAM (random access memory). The CPU performs various data processing using a work area of the RAM corresponding to an appropriate control program as a firmware piece loaded in the ROM in advance.
More specifically, the microcomputer 107 accepts a detection signal of the mark patterns from the comparison circuit 106 and outputs the detection signal outside as a magnetic tape reproduction result. Each time a mark pattern detection signal is received, all the five mark length counters 105 are reset.
The tape reproduction apparatus 100 having the aforementioned configuration can reproduce in serial the mark patterns recorded as combinations of the binary data in parallel on the magnetic tape. In this case, the tape drive unit 101 linearly moves the magnetic tape and reads the six data tracks in parallel and in serial. The six analog signals are respectively converted into digital signals by the A/D converter 102.
If the serial digital signal thus converted is "100000", the signal generation circuit 103 generates a tone signal, and otherwise, the all one signal is generated. The six binary data items successively reproduced in serial are identified as one of the five mark patterns by the mark detection circuit 104.
The mark detection circuit 104 which has identified the mark pattern outputs an enable signal to the corresponding one of the five mark length counters 105. The mark length counter 105 which has received the enable signal integrates the input lapse time as the mark pattern reproduction time.
The reproduction time integrated by the mark length counter 105 is compared to a predetermined reference time in the comparison circuit 106 connected to the counter. When the reproduction time to be integrated has reached this reference time, a mark pattern detection signal is produced to the microcomputer 107.
Here, the mark pattern detection signals produced from the five comparison circuits 106 are output by the microcomputer outside in serial. Thus, each time a mark pattern detection signal is accepted, the five mark length counters 105 are all reset.
The tape reproduction apparatus 100 having the aforementioned configuration can reproduce in serial the mark patterns recorded as combinations of parallel binary data on a magnetic tape.
However, the magnetic tape is easily worn out physically and an information recorded on it is remarkable deteriorated as the time lapses. Accordingly, there is a case that it is difficult to reproduce the information recorded. For example, before the first type mark pattern reproduction reaches the reference time, reproduction of the second type mark pattern may be started, and before the reproduction of the second type mark pattern reaches the reference time, another first mark pattern may be started. Then, two first type mark patterns are reproduced as a single pattern, and the second type mark pattern between them is not reproduced.
For example, Japanese Patent Publication (unexamined) A56-169211 discloses a magnetic tape apparatus wherein when a mark pattern is recorded on a magnetic tape, the mark pattern is reproduced simultaneously and if any defect is found in the reproduction result, the mark pattern is again recorded. That is, this technique considers only a mark pattern recording and cannot cope with a reproduction failure of a mark pattern recorded in the past.